Fix linking error for hlc.par.gc grade on Darwin.

Estimated hours taken: 3
Branches: main

Fix linking error for hlc.par.gc grade on Darwin.  The problem was that the
"-undefined suppress" option is not allowed with two level namespaces.
The solution is to use "-undefined dynamic_lookup" instead.
However this means the MACOSX_DEPLOYMENT_TARGET environment variable must be
set to 10.3 since this feature will not work on Mac OS < 10.3.  To allow
hlc.gc.par to be built on Mac 10.3, but targetted for Mac OS 10.0 - 10.2 add
a configuration option to force the use of flat namespaces (the
"-undefined suppress" option may be used with flat namespaces).

configure.in
	Add --enable-darwin-flat-namespace option.  This is the default
	for Mac OS < 10.3.  For Mac OS 10.3 two level namespaces are used
	unless this option is given.

	Set a variable to cause the MACOSX_DEPLOYMENT_TARGET environment
	variable to be set if two level namespaces are being used.

scripts/mmake.in
scripts/ml.in
scripts/mmc.in
	Set the MACOSX_DEPLOYMENT_TARGET environment variable wherever the
	linker may be called.

configure.in

@@ -2591,8 +2591,7 @@ AC_ARG_ENABLE(libgrades,
 [  --enable-libgrades=...
                           install exactly the given versions of the library.
 			  The versions are specified using a comma-separated
-			  list.
-],
+			  list.],
 enable_libgrades_given=yes;enable_libgrades="$enableval",enable_libgrades_given=no)
 
 if test "$enable_most_grades" = no; then
@@ -3227,16 +3226,56 @@ case "$host" in
 		# If the compiler is gcc then use darwin style dynamic linking.
 		# Otherwise use static linking.
 		if test "$GCC_PROG" != ""; then
+		    AC_MSG_RESULT(yes)
+		    # Check if the user has explicitly requested that flat
+		    # namespaces be used.
+		    darwin_flat_namespaces=no
+		    AC_ARG_ENABLE(darwin-flat-namespace,
+  			  [  --enable-darwin-flat-namespace  
+			  enable flat namespaces on Darwin.  This is the
+			  default for Darwin versions less than 7 (Mac OS
+			  10.3).  On versions greater than or equal to 7
+			  two-level namespaces are used by default.  This
+			  option therefore only affects Darwin versions 
+			  greater than or equal to 7.],
+		    [ darwin_flat_namespaces=yes ])
 		    SHLIB_USE_INSTALL_NAME="--shlib-linker-use-install-name"
 		    SHLIB_INSTALL_NAME_FLAG="-install_name "
-		    LINK_SHARED_OBJ="$GCC_PROG -dynamiclib -single_module"
-		    LINK_SHARED_OBJ_SH="$GCC_PROG -dynamiclib -single_module"
 		    EXT_FOR_SHARED_LIB=dylib
 		    EXT_FOR_LINK_WITH_PIC_OBJECTS=o
 		    CFLAGS_FOR_PIC="-fPIC -DMR_PIC"
 		    ERROR_UNDEFINED="-undefined error"
-		    ALLOW_UNDEFINED="-undefined suppress"
-		    AC_MSG_RESULT(yes)
+		    # Test if the Darwin version is >= 7.  If it is 
+		    # then we can use the -undefined dynamic_lookup option
+		    # and two-level namespaces.  If it isn't then we use
+		    # flat namespaces.
+		    AC_MSG_CHECKING(whether to use two-level namespaces)
+		    if uname -r | sed "s/^\(@<:@0-9@:>@*\)\..*$/\1/" | \
+		            xargs test "$darwin_flat_namespaces" != "yes" \
+			    -a 7 -le;
+		    then
+		        AC_MSG_RESULT(yes)
+			# The MACOSX_DEPLOYMENT_TARGET environment variable
+			# needs to be set when linking with two level 
+			# namespaces so we can use the
+			# `-undefined dynamic_lookup' option.
+		        SET_MACOSX_DEPLOYMENT_TARGET="\
+				MACOSX_DEPLOYMENT_TARGET=10.3; \
+				export MACOSX_DEPLOYMENT_TARGET"
+			AC_SUBST(SET_MACOSX_DEPLOYMENT_TARGET)
+		        LINK_SHARED_OBJ="$GCC_PROG -multiply_defined suppress \
+				 -dynamiclib -single_module"
+		        LINK_SHARED_OBJ_SH="$GCC_PROG -multiply_defined \ 
+				suppress -dynamiclib -single_module"
+		        ALLOW_UNDEFINED="-undefined dynamic_lookup"
+		    else
+		        AC_MSG_RESULT(no)
+		        LINK_SHARED_OBJ="$GCC_PROG -flat_namespace \
+				-dynamiclib -single_module"
+		        LINK_SHARED_OBJ_SH="$GCC_PROG -flat_namespace \
+				-dynamiclib -single_module"
+		        ALLOW_UNDEFINED="-undefined error"
+		    fi
 		else
 		    CFLAGS_FOR_PIC=
 		    EXT_FOR_PIC_OBJECTS=o

scripts/ml.in

@@ -57,6 +57,9 @@ MATH_LIB=${MERCURY_MATH_LIB="@MATH_LIB@"}
 # since @SHARED_LIBS_SH@ may refer to $MATH_LIB.
 SHARED_LIBS=${MERCURY_SHARED_LIBS="@SHARED_LIBS_SH@"}
 
+# Set the MACOSX_DEPLOYMENT_TARGET environment variable if needed.
+@SET_MACOSX_DEPLOYMENT_TARGET@
+
 # When compiling in the hlc.gc grade using the Microsoft Visual C
 # compiler, the default maximum stack size of 4Mb is too low for a
 # recursive language.

scripts/mmake.in

@@ -80,6 +80,9 @@ MERCURY_DEFAULT_GRADE=${MERCURY_DEFAULT_GRADE=@DEFAULT_GRADE@}
 MKTEMP=@MKTEMP@
 TMPDIR=${TMPDIR=/tmp}
 
+# Set the MACOSX_DEPLOYMENT_TARGET environment variable if needed.
+@SET_MACOSX_DEPLOYMENT_TARGET@
+
 MMAKE=$0
 include_makefile=
 verbose=false

scripts/mmc.in

@@ -1,7 +1,7 @@
 #! /bin/sh
 # @configure_input@
 #---------------------------------------------------------------------------#
-# Copyright (C) 1994-1998, 2000-2003 The University of Melbourne.
+# Copyright (C) 1994-1998, 2000-2004 The University of Melbourne.
 # This file may only be copied under the terms of the GNU General
 # Public License - see the file COPYING in the Mercury distribution.
 #---------------------------------------------------------------------------#
@@ -18,6 +18,9 @@ MERCURY_COMPILER=${MERCURY_COMPILER-'@LIBDIR@/bin/@FULLARCH@/mercury_compile'}
 MERCURY_CONFIG_DIR=${MERCURY_CONFIG_DIR-${MERCURY_STDLIB_DIR-'@CONFIG_LIBDIR@'}}
 export MERCURY_COMPILER MERCURY_CONFIG_DIR
 
+# Set the MACOSX_DEPLOYMENT_TARGET environment variable if needed.
+@SET_MACOSX_DEPLOYMENT_TARGET@
+
 case $# in
 	0) exec $MERCURY_COMPILER ;;
 	*) exec $MERCURY_COMPILER "$@" ;;